So im currently driving a 2004 Disco with the 4.6 motor. A few weeks back I noticed a climb in temperature and decided to pull off, add some fluid, and park it. After trying to just start it to see if anything would happen, I found it wasn't happy with running. Initially I thought it would be just the head gasket and the thermostat (due to past heating issues) so I changed about of those out, along with valve cover, intake and exhaust manifold gaskets. Before completing the process.. I realized the oil looked a bit like chocolate milk.. knowing at this point that coolant had been leaking into the engine. After changing all the gaskets and praying that the issue had been resolved.. it surely was not. When putting it back together, I did not noticed any issues with cracked cylinder heads (although that could still be an issue) or notice cracks anywhere else.. Upon being optimistic and praying that it may be a leak somewhere else, such as the timing cover gasket.. I have no other conclusions at this point. I will be tearing everything apart again next week to try and resolve this.... any ideas as to what the issue may be? Im not sure if there may be prevalent issues with the 4.6 engine... Open to any suggestions or idea.

 

When you pulled the heads off were any of the pistons really clean compared to the others?
If so you may have a crack in the aluminum block behind a liner?
But this usually doesn't get much coolant into the oil?
Most coolant into oil leaks are front cover or intake gasket related and sometimes head gaskets if they were real bad.

 

No, there was no uneven combustion or carbon build up on each piston. The head gaskets were pretty shot.. but even after I had replaced them I got a really heavy mixture. The Front Cover is definitely a possibility.. Another thought I had was the oil cooler? Im not really sure how it works as I haven't looked too much into it. The odd thing was that it all seemed to be fine until I shut it off initially. I never let it over heat, I just saw the temp gauge going up so I shut it down and dumped water into it as well as on radiator. Best case scenario its the front cover, or timing cover gasket (same thing?).. im hoping its not the cylinder heads or the block itself.

 

Did you add an oil cooler to it? The 03 & 04's didn't have them from the factory. Were you monitoring temps on a scan tool? Or just the dash cluster? The prevailing thought here seems to be that if the dash guage moves at all (at 240?) then you are already overheating.

 

Well then I guess I am completely mistaken on the oil cooler..I know they were on the D1, silly assumption on my part. Yes ive monitored temperature on OBDII while at idle
and driving. Was always in tune with dash gauge. It liked to somewhat sip coolant. I could never keep overflow reservoir full of coolant.. thus my initial thought was bad thermostat or small leak somewhere. Turned out to be leak into block somewhere. Cant seemed to find it though. I completely resurfaced cylinder heads, made sure they were as level as humanly possible. Thats not to say they still might not be cracked though.

 

Found out it was in fact the timing cover gasket.